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std::is_sorted(3)	       C++ Standard Libary	       std::is_sorted(3)

NAME
     std::is_sorted - std::is_sorted

Synopsis
	Defined in header <algorithm>
	template<  class  ForwardIt  >				     (1)  (since
     C++11)
	bool is_sorted( ForwardIt first, ForwardIt last );	      (constexpr
     since C++20)
	template< class ExecutionPolicy, class ForwardIt >

	bool  is_sorted(  ExecutionPolicy&&  policy,		     (2)  (since
     C++17)

			ForwardIt first, ForwardIt last );
	template< class  ForwardIt,  class  Compare  >			  (since
     C++11)
	bool  is_sorted( ForwardIt first, ForwardIt last, Compare (3) (constexpr
     since C++20)
	comp );
	template< class ExecutionPolicy, class ForwardIt, class
	Compare >

	bool  is_sorted(  ExecutionPolicy&&  policy,		     (4)  (since
     C++17)

			ForwardIt first, ForwardIt last, Compare
	comp );

	Checks if the elements in range [first, last) are sorted in non-descend-
     ing order.

	1) Checks if the elements are sorted with respect to
	operator<
	(until C++20)
	std::less{}
	(since C++20).
	3) Checks if the elements are sorted with respect to comp.
	2,4) Same as (1,3), but executed according to policy.
	These overloads participate in overload resolution only if

	std::is_execution_policy_v<std::decay_t<ExecutionPolicy>>    is    true.
     (until
										  C++20)
	std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>      is
     true. (since
										  C++20)

Parameters
	first, last - the range of elements to examine
	policy	     - the execution policy to use. See execution policy for de-
     tails.
		      comparison function object (i.e. an object that  satisfies
     the
		      requirements  of	Compare) which returns true if the first
     argument is
		      less than (i.e. is ordered before) the second.

		      The signature of the comparison function should be equiva-
     lent to the
		      following:

		      bool cmp(const Type1& a, const Type2& b);
	comp	    -
		      While the signature does not  need  to  have  const&,  the
     function must
		      not  modify  the	objects passed to it and must be able to
     accept all
		      values of type (possibly const) Type1 and Type2 regardless
     of value
		      category (thus, Type1& is not allowed
		      , nor is Type1 unless for Type1 a move is equivalent to  a
     copy
		      (since C++11)).
		      The  types  Type1 and Type2 must be such that an object of
     type
		      ForwardIt can be dereferenced  and  then	implicitly  con-
     verted to both of
		      them.

Type requirements
	-
	ForwardIt must meet the requirements of LegacyForwardIterator.
	-
	Compare must meet the requirements of Compare.

Return value
	true  if  the  elements in the range are sorted in non-descending order,
     false
	otherwise.

Complexity
	Given \(\scriptsize N\)N as std::distance(first, last):

	1,2) \(\scriptsize O(N)\)O(N) comparisons using
	operator<
	(until C++20)
	std::less{}
	(since C++20).
	3,4) \(\scriptsize O(N)\)O(N) applications of the comparator comp.

Exceptions
	The overloads with a template parameter named ExecutionPolicy report er-
     rors as
	follows:

	  * If execution of a function invoked as part of the  algorithm  throws
     an exception
	    and  ExecutionPolicy is one of the standard policies, std::terminate
     is called.
	    For any other ExecutionPolicy, the	behavior  is  implementation-de-
     fined.
	  * If the algorithm fails to allocate memory, std::bad_alloc is thrown.

Possible implementation
	See also the implementations in libstdc++ and libc++.

				is_sorted (1)
	template<class ForwardIt>
	bool is_sorted(ForwardIt first, ForwardIt last)
	{
	    return std::is_sorted_until(first, last) == last;
	}
				is_sorted (3)
	template<class ForwardIt, class Compare>
	bool is_sorted(ForwardIt first, ForwardIt last, Compare comp)
	{
	    return std::is_sorted_until(first, last, comp) == last;
	}

Notes
	std::is_sorted returns true for empty ranges and ranges of length one.

Example
     // Run this code

      #include <algorithm>
      #include <cassert>
      #include <functional>
      #include <iterator>
      #include <vector>

      int main()
      {
	  std::vector<int> v;
	  assert(std::is_sorted(v.cbegin(),  v.cend()) && "an empty range is al-
     ways sorted");
	  v.push_back(42);
	  assert(std::is_sorted(v.cbegin(), v.cend()) && "a range of size  1  is
     always sorted");

	  int data[] = {3, 1, 4, 1, 5};
	  assert(not std::is_sorted(std::begin(data), std::end(data)));

	  std::sort(std::begin(data), std::end(data));
	  assert(std::is_sorted(std::begin(data), std::end(data)));
	  assert(not	   std::is_sorted(std::begin(data),	 std::end(data),
     std::greater<>{}));
      }

See also
	is_sorted_until   finds the largest sorted subrange
	(C++11) 	  (function template)
	ranges::is_sorted checks whether a range is sorted into ascending order
	(C++20) 	  (niebloid)

http://cppreference.com 	   2024.06.10		       std::is_sorted(3)
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